try to do the GATEs, you can net up to 480 if you complete it (max I've seen). also be sure to buy up to the 500MGP you can get, its not much but better than starting from 0. try your hand at the daily Cactpot for a chance to win up to 10kMGP, as well as the Jumbo Cactpot that you might be able to get 1milMGP. aside from these Chocobo Races, PvP Triple Triad(til you exhaust the 180/win), and NPC Triple Triad are the only real good ways to do it. Stay away from the minigames, you'll earn no more than 15 on a win there if you're lucky(go ahead and use your free vouchers, though, just don't actually use MGP)